Tooth desensitizing oral care compositions, devices, and methods

ABSTRACT

Desensitizing oral care composition useful for treating dentinal hypersensitivity, comprising potassium oxalate and methods of use thereof. Delivery systems including a strip of material and such oral care compositions for the treatment of dentinal hypersensitivity and methods of use thereof.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application Ser.No. 61/896,361, filed Oct. 28, 2013, the entirety of which isincorporated by reference herein.

FIELD OF THE INVENTION

The present invention relates to tooth desensitizing oral carecompositions, strip-type delivery devices and methods of use wherein thecompositions contain a dentinal tubule blocker.

BACKGROUND OF THE INVENTION

Tooth sensitivity, including dentinal hypersensitivity, has becomeidentified as a common problem among consumers. Dentinalhypersensitivity is a condition where dentin is exposed due the lack ofsoft tissues covering the surfaces. The exposed dentin includes smalltubules which are susceptible to triggering of a pain response from avariety of stimuli such as heat, cold, sour taste, or pressure. Thelevel of pain can range from an ache or soreness to a shooting pain. Themost common approach for over-the-counter, at-home treatment of dentinalhypersensitivity is the use of dentifrices containing desensitizingagents such as SENSODYNE PRONAMEL (contains 5% potassium nitrate) andNOVAMIN (contains bioactive glass). While such products can provide somerelief, reduction of sensitivity through dentifrice use alone is limitedfor several reasons including: inherent limitations on the contact timeof the dentifrice to the exposed dentin (as brushing time may berelatively short); dilution of the desensitizing agent by saliva;typical usage includes rinsing one's mouth out after brushing reducingthe amount of desensitizing agent delivered to the tooth; and inherentlimitations on the amount of desensitizing agent that may be stablyformulated into a dentifrice formulation. A need therefore exists for animproved treatment for dental hypersensitivity that can be easilyperformed at home.

Oxalate salts can act as dentinal tubule blockers that can thereby beuseful for the treatment of dental hypersensitivity. Potassium oxalateis a preferred desensitizing agent as it forms calcium oxalate upondelivery to the open tubules. Formation of the calcium oxalate blocksthe dentinal tubules and may prevent environmental stimuli from causingsensitivity pain.

A product called SUPERSEAL is a commercially available dentalsensitivity treatment product available from Phoenix Dental. TheSUPERSEAL product is in liquid form and is sold in a small bottle. Thebottle contains a 2.9% solution of a potassium oxalate salt,K3H(C2O4)*2H2O at a pH of 1.5 (approximately 1.0% of oxalate ion). Theinstructions for use include painting or swabbing the liquid in the oralcavity. Although the product does help with dental hypersensitivity, itcan be difficult for consumers to know how much to apply and/or totarget a single area for treatment, and contact time of the potassiumoxalate at the sensitivity site may be transient due to dilution withsaliva.

Similarly, a LISTERINE brand rinse is commercially available in theUnited Kingdom that contains dipotassium oxalate and has a pH of 4.3.Again, the presence of the potassium oxalate in the mouth is transientand here, it is considerably difficult to target a particular area ofsensitivity with a rinse product.

The combination of adhesive-building polymer with potassium oxalate hasbeen attempted in another commercial tooth desensitizing product,SENZZZZZAWAY, available from Majestic Drug (New York, USA). SENZZZZZAWAYis a single-use blister packed product containing a composition thatincludes a CARBOPOL (CARBOPOL is the trade name for a general class ofhigh molecular weight homo and co-polymers of acrylic acid crosslinkedwith a polyalkenyl polyether, commercially available from LubrizolAdvanced Materials, Inc. (Ohio, USA), thickener and 2.5% (as added) ofan oxalate salt (KHC2O4+HNO3) at a pH of 0.7. The product is packagedwith a small brush and the instructions include brushing the productonto the area to be treated. If potassium oxalate is applied to thewrong part of the oral cavity and/or for too short of a period of time,it is possible that no benefit is garnered or that the crystaldeposition occurs at the wrong site. A need therefore still exists for asensitivity product that can reach the desired location, deliver thedesired chemistry, and for the desired amount of time. The priorliterature discloses that potassium oxalate works but also has disclosedit as being ineffective for dentinal tubule blocking. Without beinglimited by theory, it is now believed that some of the ineffectivenesswas wrongly associated with the potassium oxalate mechanism itself whenit was likely just the wrong selection of contact time, delivery device,pH, and the like.

Strip-form oral care delivery systems are commercially available, suchas tooth-whitening strips including those sold under the name CRESTWHITESTRIPS by the Procter & Gamble Company (Cincinnati, Ohio, USA). Thepopularity of the strip format has expanded to include strips forfluoride treatment and sensitivity treatment (for example, SHEER FLUORXand SHEER DESENZ strip tooth treatment products, both commerciallyavailable from the CAO Group, Utah, USA).

Further, the literature discussing delivery systems for tooth-whiteningalso often generally disclose that the same delivery systems may be usedwith sensitivity agents. However, due to the fundamental differencesbetween whitening agents and potassium oxalate, it has been surprisinglyfound that the compositions previously found to be useful in conjunctionwith whitening strip products are unsuitable for the delivery ofpotassium oxalate.

A tooth sensitivity delivery kit including a preformed tray and a bulkyfoam strip (approximately 6 cm long, 1 cm tall, 1 cm thick) impregnatedwith a potassium oxalate solution that sits inside the tray iscommercially available under the trade name REMESENSE from Sylphar(Belgium). Although providing some efficacy, the REMESENSE tray systemis bulky and uncomfortable for consumers during use. Further, due to theporosity of the impregnated foam, the potassium oxalate solution settles(due to gravity) into the lowest portion of the foam, making applicationto the gum line difficult (if not impossible) and the delivery systemonly suited for use with the upper arch, not the lower arch. Further, itis difficult to provide targeted relief to an area in need of treatmentthrough the use of the REMESENSE tray and foam.

The need therefore exists for a dentinal hypersensitivity treatmentproduct that can provide directed, sustained delivery of a desensitizingagent to a desirable area in the oral cavity, for a period of timesufficient to provide significant tubule blockage and subsequentsensitivity relief.

SUMMARY OF THE INVENTION

Without being limited by theory, it has surprisingly been found thatstrip-type delivery systems can provide directed, sustained delivery ofa desensitizing agent to a desired area in the oral cavity, for a periodof time sufficient to provide significant tubule blockage and subsequentsensitivity relief.

In some aspects, the present invention relates to desensitizing oralcare compositions useful for treating dentinal hypersensitivity,including a) at least 40%, by weight of the composition, of water; b)from about 0.01% to about 25%, by weight of the composition, of adesensitizing agent selected from oxalic acid, salts of oxalic acid, andmixtures thereof; c) from about 0.1% to about 30%, by weight of thecomposition, of an adhesive polymer thickener; d) from about 0.5% toabout 40%, by weight of the composition, of a secondary structuringpolymer thickener; e) optionally from about 10% to about 40%, by weightof the composition, of a humectant; f) less than 0.1%, by weight of thecomposition, of abrasive; wherein the composition has a pH of less than10.

The present invention further relates to such compositions wherein thecomposition exhibits a delta angle value of less than about 35°; and/orwherein the complex modulus is according to Equation 1.

The present invention further relates to delivery systems for suchdesensitizing oral care compositions comprising: a) a strip of material;a desensitizing oral care composition; and optionally a release liner.

The present invention further relates to such delivery systems whereinthe desensitizing oral care composition comprises: from about 50% toabout 65%, by weight of the composition, of water; from about 1% toabout 5%, by weight of the composition, of a desensitizing agentselected from oxalic acid, potassium salts of oxalic acid, and mixturesthereof; from about 0.5% to about 10%, by weight of the composition, ofan adhesive polymer thickener; from about 1% to about 20%, by weight ofthe composition, of a secondary structuring polymer thickener; fromabout 25% to about 40%, by weight of the composition, of a humectant;and less than 0.1%, by weight of the composition, of abrasive; and arelease liner comprised of polypropylene film.

The present invention further relates to such compositions and deliverysystems wherein the humectant comprises glycerin.

The present invention further relates to such compositions and deliverysystems wherein the composition comprises a Delta angle less than 30°and greater than 15°.

The present invention further relates to such compositions and deliverysystems wherein the composition comprises the secondary structuringpolymer in an amount equal to or greater than the amount ofadhesive-building polymer.

The present invention further relates to such compositions and deliverysystems wherein the ratio of the adhesive polymer to the secondarystructuring polymer is from about 1:1 to about 1:5.

The present invention further relates to such compositions and deliverysystems wherein the composition comprises from about 1% to about 6% ofthe desensitizing agent.

The present invention further relates to such compositions and deliverysystems wherein the desensitizing agent is selected from potassiumoxalate salts and mixtures thereof.

The present invention further relates to such compositions and deliverysystems wherein the adhesive-building polymer is selected from highmolecular weight homo and co-polymers of acrylic acid crosslinked with apolyalkenyl polyether, and mixtures thereof.

The present invention further relates to such compositions and deliverysystems wherein the secondary structuring polymer is selected fromcarboxymethylcelluloses and mixtures thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graphical representation of Example I plotting the ComplexModulus versus the Delta values for the compositions shown in Tables 1A,1B, 1C, 1D, 2A and 2B. The solid black line represents Equation 1 andthe dashed black line represents Equation 2.

FIG. 2 is a schematic side view of an exemplary, multi-layer strip.

FIG. 3 is the silhouette of an exemplary strip of material.

FIG. 4 is a schematic view of an exemplary release liner.

FIG. 5 is a schematic view of an exemplary release liner.

FIG. 6 is a schematic view of an exemplary release liner.

FIG. 7 is a top view of an experimental apparatus as described inExample 3.

FIG. 8 is a schematic side view of an experimental apparatus asdescribed in Example 3.

FIG. 9 is a graphical representation of Flow Reduction vs. pH, asdescribed in Example 4.

DETAILED DESCRIPTION OF THE INVENTION

In some aspects, the strip-type delivery systems disclosed include astrip of material, a desensitizing oral care composition, and optionallyinclude a release liner. The desensitizing oral care compositions mayinclude a desensitizing agent, an adhesive-building polymer, a secondarystructuring polymer, and water. Methods of using such delivery systemsare also described. These delivery systems and methods, as well as otheroptional components are discussed more fully, below. Again without beinglimited by theory, oxalates may be a preferred anti-sensitivity agent asthey form calcium oxalate upon delivery to the open tubules. Formationof the calcium oxalate blocks the dentinal tubules to preventenvironmental stimulus from causing sensitivity pain. The overall designof the strip-type delivery system which applies oxalate is important toproduct performance, stability, application and manufacturability.

Delivery System

Delivery systems useful for applying a desensitizing agent to the oralcavity may include a strip of material, a desensitizing oral carecomposition, and, optionally, a release liner.

The strip of material may have at least two sides. The desensitizingoral care composition may be applied to at least one side of the stripof material, and, optionally, a release liner is applied to protect thecomposition during storage and/or transportation.

Without being limited by theory, it is believed that in order toeffectively deliver the desensitizing agents, it is important to selectan appropriate strip of material, appropriate oral care compositionalelements, and appropriate rheological characteristics of the compositionto ensure that the delivery system is a) stable during storage andshipment; b) that the desensitizing agent releases from the compositionto the targeted area; c) that the delivery device adheres to the desiredlocation in the oral cavity for the desired period of time; and/or d)when a release liner is used, that the strip and composition cansufficiently release from the liner without leaving more than half ofthe composition behind.

Strip of Material

The delivery system may include a strip of material. As used herein,“strip of material” generally refers to section of thin material havinga length longer than the width, and a thickness less than the width. Anexample is a length from about 2 to about 3 times the width.Alternatively, the length may be from about 1 cm to about 10 cm, and thewidth may be from about 0.1 cm to about 10 cm. Alternatively the widthmay be from about 0.25 to about 5 cm, alternatively from about 0.25 toabout 2 cm, alternatively from about 0.75 to about 2 cm, alternativelyabout 1 cm. In an example, the length is from about 1 to about 5 cm,alternatively from about 2 to about 5 cm.

While the thickness of the film may vary, the film may have a thicknessbetween about 0.1 micrometer and about 1500 micrometers (μm).

The strip of material may serve as a protective barrier for thedesensitizing oral care composition. It may prevent substantial leachingand/or erosion of the desensitizing oral care composition for a selectedperiod of time, or altogether. Such leaching and/or erosion could becaused, for example, by contact between the composition and the wearer'slips, tongue, or saliva. Preventing substantial leaching or erosionallows the active in the desensitizing oral care composition to act uponthe oral surface for an extended period of time, from several seconds toseveral hours. The term “act upon” is herein defined as bringing aboutthe deposition of oxalate and oxalate-containing precipitates orcrystals on the surface to be treated (including dentin, enamel,pellicle, and smear layers, or combinations thereof). “Act upon” caninclude formation of oxalate crystals in the dentinal tubules.

Although strip-type delivery systems have now become common fortooth-whitening, it should be understood that the usage of such deliverysystems for delivering desensitizing agents is different in severalregards. The selection of the appropriate strip materials issurprisingly different. It is contemplated that some strips of materialwill be preferred over others for reasons of application and wearabilitydepending on the desensitizing oral care composition used.

Unlike in whitening strips, where the whitening target surface ispredominantly the teeth, treating dentinal hypersensitivity typicallyinvolves treating oral surfaces at or near the gumline, where theexposed tubules typically reside. To ensure good coverage of thegumline, the strip can therefore be sized to cover a portion of the softgingival tissue and a portion of the harder tooth tissues (enamel and,if present, exposed dentin). It may not be critical to cover all of theharder tooth tissues to effectively reduce sensitivity. The region ofapplication can be anywhere on the upper or lower dental arch and istypically (although not always) on the buccal surfaces (cheek side).Because some of the regions of sensitive teeth are in the posteriorregions (back teeth) it becomes much easier to apply the strip if onehand can be used to hold and apply the strip while the other hand isused to pull back the lip and cheek areas and apply the strip directly.Holding the strip with one hand and applying it requires the strip tohave sufficient stiffness to handle and hold it, yet still posses enoughflexibility to conform to the shape of the tissues and teeth the stripis being applied to. As a result, there is an optimum range of stripphysical properties which result in good handling and conformability tothe sensitivity surfaces being treated, and these properties do notnecessarily correlate to the properties desirable for delivering otherkinds of oral care compositions. The preferred flexural stiffness andsize/shape of the strip used in the disclosed delivery systems are insome aspects different than those typically used for whitening stripproducts.

The delivery system may be sized to cover a large portion, or even theentire maxillary or mandibular gumline. Many people experiencesensitivity in fewer than all of their teeth. Therefore, it may beuseful to provide a delivery system sized to cover less than most of themaxillary or mandibular gumline, such as about half of the maxillary ormandibular gumline, or even less than half of the maxillary ormandibular gumline.

The delivery system may include a strip of material comprising atextured film. The film may be textured on one side and flat, oruntextured, on the other side. The desensitizing oral care compositionmay be applied to the flat side.

The delivery system may include a strip of material that is conducive tobeing cut by a rotary die on a release liner, through a process called“kiss cutting.” In a kiss cutting process, it may be desirable to cutthe film without cutting completely through the release liner duringprocessing.

The strip of material may be a solid layer, or may have pores, channels,or other openings that run from one side of the strip to an opposite,facing side of the strip. The strip of material may be water-permeableor water-impermeable. For example, if the composition requires hydrationfor improved efficacy or distribution, a water-permeable material may bedesirable. A strip of material is water-permeable if water can passthrough the material at a rate of at least 0.5 g/cm2/hour.

Material

Materials useful for the strip of material include a wide variety ofmaterials, and can be in a single layer, or multiple layers, or can bein an irregular pattern of layers. As examples, the material may be amesh or otherwise have gaps or holes in the layer. The material may beformed with gaps or holes, or may be punctured or otherwise processed ortreated to create gaps or holes in the layer.

The strip of material can be dissolvable. In multi-layer materials, oneor more portions or layers of the strip may be dissolvable. Inmulti-layer materials, one or more portions or layers of the strip maybe dissolvable, and other portions or layers of the strip may beindissolvable. If more than one dissolvable portion or layer is present,some portions or layers may dissolve at a different rate than otherportions or layers. Exemplary dissolvable materials are described, forexample, in U.S. Patent Application Publication 2005/0208110.

The strip may be multi-layered and dissolvable at least in part todeliver agents sequentially to the oral cavity. As a non-limitingexample, a potassium oxalate-containing inner layer may be combined witha calcium chloride-containing middle- or outer layer. FIG. 2 shows aschematic side view of a multi-layer strip having an inner layer 10, amiddle-layer 20, and an outer layer 30. It should be understood that ina physical strip, distinct layers may be difficult or impossible tovisualize with the naked eye, particularly if one or more of the layersis very thin, or if the layers have similar visual appearance. As usedherein, an “inner” refers to a position nearer the teeth and/or gumswhen the strip is applied in the mouth as intended, and “outer” refersto a position nearer the cheek or further from the teeth and gums whenthe strip is applied in the mouth as intended. An inner layer need notbe (but could be) the innermost layer of the strip of material, just asan outer layer need not be (but could be) the outermost layer of thestrip of material. As used herein, the relative positions of inner andouter layers are described at the time of application, before any layershave dissolved (if dissolvable layers are used), unless expressly statedotherwise.

Upon application to the teeth and gums, the potassium oxalate-containinginner layer may dissolve first, releasing oxalate into the tubule fluidof open tubules. In some embodiments, the dissolution of the potassiumoxalate-containing inner layer may not be required to deliver theoxalate to the tubule fluid. For example, oxalate may diffuse from theinner layer, and the dissolution of the inner layer may expose anotherlayer or layers. The calcium chloride-containing middle- or outer layermay dissolve after the potassium oxalate-containing inner layer,releasing calcium near the tubule. The release of calcium near thetubules recently treated with oxalate can further the formation ofocclusive calcium oxalate crystals in or near the tubules, which in turnmay decrease sensitivity associated with open tubules. As with the innerlayer, it may not be essential for the calcium chloride-containing outerlayer to dissolve at all, or it may not be essential for the calciumchloride-containing outer layer to dissolve in order to deliver calciumin or near the tubules.

By modifying the strip of material composition, size, and layers, thedelivery of the desensitizing agent may be modified.

The strip of material may comprise polymers, natural and synthetic wovenmaterials, non-woven materials, foil, paper, rubber, or combinationsthereof. The material may be selected from films and may include one ormore polymers. Non-limiting, exemplary polymers useful in the strip ofmaterials include polyolefins (e.g. polyethylene), ethylvinylacetate,polyesters, ethylvinyl alcohol, and combinations thereof. Examples ofpolyesters include Mylar® and fluoroplastics such as Teflon®, bothmanufactured by DuPont. In some embodiments, the strip of material maycomprise polyethylene. The strip of material may comprise a blend ofhigh density and low density polyethylene. An exemplary blend of highdensity and low density polyethylene is a combination of about 90% HDPEwith about 10% LDPE.

The strip of material may be formed by a cast or blown process. In somepreferred embodiments, the strip of material is cast. Casting mayprovide better control over the caliper of a film of certainthicknesses. The strip of material may be embossed with a pattern ortexture, such as an array of pyramid shapes. Such textures may providetactile feedback to a user, and may make it easier to place or confirmthe placement of the strip, especially, but not exclusively, if thestrip is translucent, transparent, or otherwise difficult to see againstthe teeth. The strip of material may have about 25-35 grams of polymerper square meter of film. The strip of material is generally less thanor equal to about 1 mm thick, preferably less than about 0.05 mm thick,and more preferably from about 0.001 to about 0.03 mm thick. Apolyethylene strip of material is preferably less than about 0.1 mmthick and more preferably from about 0.005 to about 0.02 mm thick.

The shape of the strip of material is any shape and size that covers thedesired oral surface. Preferably the strip of material has roundedcorners. As illustrated in an exemplary embodiment in FIG. 3, roundedcorners 40 are defined as not having any sharp angles or points 50.Rounded corners may help avoid gum irritation that may occur with sharpedges. In some embodiments, all corners of the strip of material arerounded. In some embodiments, corners of the strip of material intendedto contact the gums or other soft tissues are rounded.

The strip of material may contain shallow pockets. When thedesensitizing oral care composition is coated on a strip of material,additional oral care composition fills shallow pockets to providereservoirs of additional oral care composition. Additionally, theshallow pockets may help to provide texture to the delivery system. Thefilm may have an array of shallow pockets. Generally, the shallowpockets, if used, are approximately 0.4 mm across and 0.1 mm deep. Theshallow pockets may be formed within a particular layer of the strip ofmaterial, or may be formed by layering two or more materials, e.g., bylayering a mesh over another layer.

When shallow pockets are included in the strip of material and oral carecompositions are applied to it in various thicknesses, the overallthickness of the delivery system is generally less than about 1 mmPreferably, the overall thickness is less than about 0.5 mm.

Usage and Making

The strip of material may be held in place on the oral surface byadhesive attachment provided by the desensitizing oral care composition.The viscosity and general tackiness of the desensitizing oral carecomposition cause the strip of material to be adhesively attached to theoral surface without substantial slippage from the frictional forcescreated by the lips, teeth, tongue and other oral surfaces rubbingagainst the strip of material while talking, drinking, etc. However, theadhesion to the oral surface should be low enough to allow the strip ofmaterial to be easily removed by the wearer by simply peeling off thestrip of material using one's finger or fingernail, or by rubbing thestrip of material with a soft implement, such as cotton balls, swabs orgauze pads.

Strips may be used at least twice, or at least three times, or at leastup to five times, for best effect. A new or fresh strip may be used foreach treatment. Repeated deposition of oxalate, for example, has beenshown to significantly reduce flow rates through dentin, as measured byExample 3, below, which should correlate to significantly reducedsensitivity in vivo.

The strip of material may be formed by several of the film makingprocesses known in the art. In some embodiments, a strip of materialmade of polyethylene is made by a blown process or a cast process. Otherprocesses, including extrusion, are also feasible. Additionally, thedesensitizing oral care composition may be incorporated onto the stripduring the processing of the strip. The desensitizing oral carecomposition may be a laminate on the strip.

Size and Shape of the Strip of Material

Strips having a shorter length can be less rigid than longer strips dueto the handling during application. Rigidity can be measured as flexuralstiffness, using a Handle-O-Meter instrument, available fromThwing-Albert Instrument Co. of Philadelphia, Pa. (such as model#211-300, or equivalent), according to ASTM test method D2923-95. Thestrip of material may have a flexural stiffness less than about 50grams/centimeter. Strips in the range of 1-5 cm in length are preferredfor application to the posterior dentition, if application to theposterior dentition is desired. Shorter strips may be most useful wheresensitivity is localized to a tooth or a small number of teeth. Longerstrips may be most useful where sensitivity occurs at multiple teeth, orwhere the user is uncertain precisely where (e.g., which tooth or partof a tooth) the sensitivity originates. This is different from stripsfor whitening or other cosmetic purposes, which may be applied only tothe most visible teeth at the front of the mouth. For cosmetic purposes,the range of coverage desired is typically much smaller than it might befor sensitivity reduction. Further, the handling properties of asensitivity strip do not necessarily match those of a strip for cosmeticpurposes, since a sensitivity strip may be applied to the back teeth,where soft tissues may interfere with application of the strip.

The width of the strip may also contribute to ease of handling andapplying the strip. Without being limited by theory, if the strip is toowide, less stiff strip materials may tend to curl over on themselveswhile being handled. This may require straightening the strip before itcan be applied, or, if the strip tends to adhere to itself, curling backon itself may render the strip unusable. Excessively wide strips mayalso tend to extend beyond the intended treatment surface into areaswhich cause the strip to contact the connective soft tissue which joinsthe cheeks with the gingiva. If the strip extends into this u-shapedconnective soft tissue region, it becomes more difficult for the stripto conform to the target treatment surfaces and remained adhered due tothe differences in geometry and rates and directions of motion. The softgingiva do not move whenever the mouth moves, while the cheek tissues dotypically move when the mouth moves. This can cause the strip to bepulled in multiple directions, leading to loss of adhesion. Ultimately,the strip may be loosened and/or displaced from the target treatmentsurface or surfaces. Strips in the width range of 0.25 cm to 2 cm canwork. Strips in the width range of 0.75 cm. to 1.5 cm appear to beoptimal for polyolefin materials for this purpose. It should beunderstood that sizing is also a function of material choice for thestrip of material. For posterior teeth, a preferred strip is sized andhas sufficient stiffness to be handled by one hand while also beingsized and be sufficiently flexible to be applied to the gumline ofsensitive teeth without causing the strip to become dislodged.

Visual and Tactile Aspects of the Strips

Particularly on the posterior teeth, users may desire the ability to seethe strip after the strip is applied, so they can visually confirm thestrip placement. In some embodiments, the entire strip of material maybe readily visible. For example, the strip of material may compriseopacifiers (such as mica, titanium dioxide, other inert opacifiers, andcombinations thereof); colored strip material; translucent stripmaterial; textured strip material; designs or artwork on the strip; orcombinations thereof. In some embodiments, some portions or layers ofthe strip of material are readily visible, and others are not. Forexample, the portions of the strip intended to cover posterior teeth andadjacent gingiva may be readily visible. Portions of the strip intendedto cover anterior teeth, particularly those teeth routinely visible toothers, may be less visible (e.g., transparent or tooth-colored). As analternative to visual confirmation, a strip of material with a textureenables consumers to confirm with their tongues that the strip is inplace during the treatment time.

The strip of material may have a pastel color due to the inclusion of afood safe dye, or a blue color due to the inclusion of a blue food-safedye, or both (e.g., in different portions or layers of the strip).Without being limited by theory, the use of pastel and/or blue hues maycommunicate to users that the product is gentler to the soft tissuesthan strips of other colors.

Desensitizing Oral Care Composition

Suitable desensitizing oral care compositions include a desensitizingagent, an adhesive-building polymer, a secondary structuring polymer,and water. As used herein, “oral care composition” means compositioncomprising a desensitizing agent, an adhesive-building polymer, asecondary structuring polymer, water, and, optionally, other components.An oral care composition may be homogenous, but does not have to behomogenous. The oral care composition components may be in the samephase or in separate phases, in a suspension, in laminates, dots,stripes, patterns, etc., as long as they interact sufficiently tosustainably provide the agent to the desired treatment location for asufficient period of time.

The desensitizing oral care composition may optionally further containother components such as additional oral care actives, such as fluoridesalts, stannous salts, zinc salts, whitening agents, bluing agents, andcombinations thereof; pH modifiers or buffers; humectants; plasticizers;flavors; sensates; rheology modifiers; TREK agonists; aestheticparticles; abrasive particles; or combinations thereof. TREK-1 channelscontrol pain produced by mechanical stimulation. The TREK-1 channel hasbeen linked to the TRPV1 pain response. TREK-1 potassium channel(TREK-1) agonists drive positive consumer perception from productscontaining them. The TREK-1 agonists further drive enhanced reduction intooth sensitivity and/or oral discomfort, thus providing an oral comfortsensation. TREK-1 agonists include: L-carvone; gamma-dodecalactone;4-ethyloctanoic acid; 2-Isopropyl-5-methyl-2-hexenal; 4-Methylnonanoicacid; trans-2-Decenal; Tributyl Phosphate; Dioctyl Adipate; Bis(2-ethylhexyl) Phosphate; Spearmint oil; Synthetic Cassia; Methyl salicylate;Wintergreen oil; Thymol; Eugenol; and combinations thereof.

Delta Angle

Delta angle (δ) is the phase lag between the applied and resultingstress and strain. The delta angle is related to the storage and lossmoduli via equation 4. A completely elastic solid will have a deltaangle of 0 degrees (°), that is, the stress and strains will beperfectly in phase. A completely viscous fluid will have a delta angleof 90°, that is, the stress and strains will be perfectly out of phase.Viscoelastic materials have delta angles between 0° and 90°.G*=G′+iG″  (Equation 3)Tan δ=G″/G′  (Equation 4)

The desensitizing oral care compositions herein exhibit a delta anglevalue of less than or equal to about 35°, preferably less than or equalto about 32°, preferably less than or equal to about 30°, preferablyless than 30°. In an example, the delta angle is further greater than orequal to about 5°, alternatively greater than or equal to about 10°,alternatively greater than or equal to about 12°.

Complex Modulus

Complex modulus (G*) is the combined storage modulus (G′) and lossmodulus (G″) according to equation 3. The complex modulus ofviscoelastic compositions is often measured by applying a cyclic stress(or alternatively a cyclic strain) and measuring the resulting cyclicstrain (or resulting cyclic stress). The oral care compositions have acomplex modulus that is greater than or equal to 1700 multiplied by e(inverse log) raised to the power of (−0.05 multiplied by the deltaangle value), see Equation 1. In an example, the complex modulus isequal to or greater than about 2100 multiplied by e to the power of(−0.05 multiplied by the Delta angle value), see Equation 2.Complex Modulus≧1700e ^((−0.05 Delta Angle))  (Equation 1)Complex Modulus≧2100e ^((−0.05 Delta Angle))  (Equation 2)

The viscoelastic properties of the oral care composition, such as thedelta angle value and complex modulus of the composition, can beparticularly important when the delivery system includes a releaseliner. If the desensitizing oral care composition fails to peel off ofthe release liner, or only peels off in part, the user will be unable toapply the strip of material and composition to the oral cavity or willexperience limited efficacy. It is preferred that at least fifty percent(50%), alternatively at least 75%, alternatively at least 90%, or more,of the composition peels off the release liner when the strip ofmaterial and desensitizing oral care composition are about 3 cm long andare grasped and removed from the release liner by the fingers (such as aconsumer would do when preparing to use the delivery system) at a rateof approximately 3 cm/sec.

The desensitizing oral care composition can be in the form of a viscousliquid, paste, gel, semi-solid, gummy, or other suitable form that canprovide sufficient adhesion. Preferably, the composition is in the formof an aqueous gel. The composition may have a viscosity of from about200 to about 1,000,000 cps at low shear rates (less than 1 s⁻¹).Preferably, the viscosity is from about 30,000 to about 800,000 cps andmore preferably from about 100,000 to about 600,000 cps.

The desensitizing oral care composition may be applied to the strip ofmaterial by coating the entirety or a portion of the strip, and may beapplied in a pattern (such as stripes, spots, geometric patterns, orother designs) or in layers, or in combinations thereof. For example,some portions of the strip may be coated with a substantiallycontinuous, homogenous layer, and other portions of the strip may becoated in patterns and/or multiple layers. In some embodiments, thecomposition is applied to at least one side of the strip of materialsuch that the strip of material includes from about 0.0005 to about 0.1grams/cm² of the composition, alternatively from about 0.001 to about0.05 grams/cm2 of the composition, or from 0.01 to 0.04 grams/cm². Thecomposition may be applied to only one side of the strip of material.

It is also contemplated that the composition can be applied to the teethand/or soft tissues of the oral cavity with an applicator (e.g. a brush,swab, or sponge). The composition can then optionally be covered with apiece or strip of material.

One example of a preferred adhesive oral care composition is oneincluding CARBOPOL thickener, carboxymethylcellulose polymer, potassiumoxalate, water, and glycerin.

Desensitizing Agent

The desensitizing oral care compositions disclosed may include adesensitizing agent. Exemplary desensitizing agents include oxalic acid,salts of oxalic acid, and mixtures thereof. Preferred salts of oxalicacid include the potassium salts of oxalic acid. A potassium salt ofoxalic acid may be selected from dipotassium oxalate (CAS No. 127-96-8),potassium oxalate dehydrate (CAS No. 6100-20-5), potassium tetroxalatedehydrate (C4H7KO10), dipotassium oxalate monohydrate (CAS No.6487-48-5, K2C2O4*H2O), and combinations thereof. Dipotassium oxalatemonohydrate is commercially available in a water carrier as CAS No.583-52-8 (equivalent to CAS No. 6487-48-5 plus CAS 7732-18-5 for thewater carrier). In some embodiments, the desensitizing agent is selectedfrom K2C2O4*H2O, K3H(C2O4)*2H2O, and mixtures thereof.

In some embodiments, the composition includes from about 0.01% to about25%, alternatively from about 0.1% to about 25%, alternatively fromabout 0.05% to about 25%, alternatively from about 0.5% to about 15%,alternatively from about 1% to about 20%, alternatively from about 1% toabout 10%, alternatively from about 1% to about 5%, alternatively fromabout 2% to about 5%, alternatively from about 2% to about 4%, by weightof the composition, of the desensitizing agent. In an example, thedesensitizing oral care composition contains from about 2.5% to about3.5%, by weight of the composition, of the desensitizing agent.

Additional compounds useful for reducing tooth sensitivity may beincluded in addition to the desensitizing agent. For example, thecomposition could further include a supplementary anti-sensitivity agentselected from other potassium salts, such as potassium nitrate,potassium chloride, potassium citrate, and combinations thereof; astannous ion source such as stannous fluoride, stannous chloride, andcombinations thereof; a strontium ion source such as a strontium salt; azinc ion source such as a zinc salt; arginine; capsaicin; 2-hydroxyethylmethacrylate (HEMA); eugenol; a bioactive glass; arginines, for example,sodium arginine or arginic acid; fluoride ion sources; calcium ionsources; or any combination thereof. Additional compounds can includepolymeric agents which can serve as both thickening agents and occludingagents—calcium-reactive polymers, e.g. alignates, work well for thispurpose.

Water

The desensitizing oral care compositions may include at least 40% water,preferably at least 50%, more preferably at least 55%, by weight of theoral care composition, of water. The composition may contain from about40% to about 95%, alternatively about 50% to about 95% water. Thisamount of water includes any free water that is added to thecomposition, plus that amount of water that is introduced with othermaterials.

Without being limited by theory, it has been observed that the level ofwater in the composition is important to achieve the desired dentinaltubule occlusion and resulting desensitizing benefit. Typically, apolymeric adhesive composition high in water content exhibits loweradhesiveness than the same composition with lower water. However,compositions with high water deliver oxalate much more effectively. Infact there is a decline in efficacy as the water content of theoxalate-containing composition declines. Further, without being limitedby theory, lower water content can lead to the oxalate active beingbound in the matrix and also result in a high counterflux of water outof the dentin, offsetting the delivery of the oxalate to the tubule.Generally, compositions containing less than 50% water do noteffectively deliver oxalate as measured by the Pashley method, or,alternatively, the method of Example 3, which is a functional equivalentof the Pashley method. On the other hand, if the composition is too highin water, the composition may not be able to hold the strip in place forthe desired contact wear time. Hence, there is a balance between theadhesiveness, water content and occlusion efficiency.

pH

In the literature, it is reported that some oxalate compositions workwhile others provide marginal efficacy at best. Upon examination of thisinconsistent data, it is theorized that compositions with lower pHperform better than compositions with high pH. Some of the reports ofpoor performance may have been associated with compositions having anineffective pH. However, given sufficient contact time, even higher pHcompositions may provide good efficacy. Hence the pH of the compositionwill be considered when determining the required wear time, which inturn informs the desired properties of the adhesive matrix.

The pH of the composition may be less than about 8, alternatively fromabout 0.5 to about 8, alternatively from about 1 to about 7,alternatively from about 1.5 to about 6.0, alternatively from about 5.0to about 5.4, alternatively about 5.2, alternatively less than about 4.For some deposition agents, a pH change of 0.1 units may be significant.In some embodiments, the pH of the composition may be about 1.1 to 6.9,or about 1.1 to about 3.0. The pH measurement should be taken aftermaking the composition, before the product is packaged. A lower pH isgenerally more desirable, with lower pH most helpful with certain saltsand/or reduced contact time between the strip and the sensitive tissues.

pH Adjusting Agent

The desensitizing compositions may optionally include a pH adjustingagent to improve the storage stability of the composition or to make thesubstance gentle for oral hard and soft tissues, or both. These pHadjusting agents, or buffers, if used, can be any material which issuitable to adjust the pH of the oral care composition. Exemplary pHadjusting agents include sodium bicarbonate, sodium phosphate, sodiumhydroxide, ammonium hydroxide, sodium stannate, triethanolamine, citricacid, hydrochloric acid, sodium citrate, silica, and combinationsthereof. When used, the pH adjusting agents are generally present in anamount of from about 0.001% to about 10%, preferably from about 0.05% toabout 5%, by weight of the oral care composition.

Polymers

The desensitizing oral care compositions herein include anadhesive-building polymer and a secondary structuring polymer.

Without being limited by theory, it has surprisingly been found that abalanced combination of an adhesive polymer and a secondary structuringpolymer further in combination with the appropriate amount of water anddesensitizing active can be established by selecting the compositionalelements according to those capable of meeting the preferred range ofrheological conditions. Compositions of relatively high water contentare typically not very adhesive, and may not provide suitable adhesionof the strip to sensitive teeth or tissues. Underhydrated polymers ofthe same type may be more adhesive, but may not be stable during storageor may delay the release of desensitizing agents from the polymer. Usinga combination of an adhesive polymer and a secondary structuring polymerresolves this dilemma.

Further without being limited by theory, it has been surprisingly foundthat by selectively balancing the amount and grade of at least twopolymers, each having the capability to hydrogen bond and, the first, anadhesive thickening polymer having a higher density of carboxyl groupsthan a second structuring polymer, that targeted delivery of thedesensitizing agent to the oral cavity can be made for a desirableperiod of time.

Adhesive-Building Polymer

The desensitizing oral care compositions may include from about 0.1% toabout 30%, by weight of the composition, of an adhesive-buildingpolymer. The compositions may contain from about 0.5% to about 20%,alternatively from about 0.5% to about 10%, alternatively from about 1%to about 5%, alternatively from about 2.25% to about 10%, alternativelyfrom about 2.25% to about 6%, by weight of the composition, of theadhesive-building polymer.

As used herein, “adhesive-building polymer” refers to the general classof polymers capable of modifying the viscosity of a composition as wellas providing adhesive properties, preferably muco-adhesive properties,to the composition, either alone or in combination with othercomposition components. Adhesion to both hard and soft oral tissues (atleast temporarily) is desirable. Such polymers are capable of hydrogenbonding, contain polar or charged groups and are hydrophilic. One ofordinary skill will understand that the level of adhesive properties canbe varied to provide adhesion for longer or shorter periods of time inthe oral cavity, depending on the desired application time. Someadhesive polymers, like PVP, may also require polyols to help buildadhesiveness.

The composition may be coated onto a strip of material and may becapable of sufficiently holding the strip and the composition againstthe hard and/or soft tissues of the oral cavity for a period of time.That period of time may be at least 0.5 minutes, alternatively at least5 minutes, alternatively at least 10 minutes, alternatively at least 15minutes. The period of time may be from about 5 minutes to about 2hours, alternatively from about 5 minutes to about 1 hour, alternativelyfrom about 10 minutes to about 30 minutes, alternatively overnight(e.g., 6-12 hours, or 6-10 hours, or approximately 8 hours).

Adhesive-building polymers useful herein include polycarboxylic acidsselected from carboxypolymethylene resins.

Carboxypolymethylene is a slightly acidic vinyl polymer with activecarboxyl groups. Carboxypolymethylene resins useful herein include thosecommercially available under the trade name CARBOPOL. CARBOPOL is thetrade name for a general class of high molecular weight homo andco-polymers of acrylic acid crosslinked with a polyalkenyl polyether.Such polymers are commercially available from Lubrizol (Ohio, USA).Pharmaceutical grade carboxypolymethylene resins are particularly usefulherein.

An example adhesive polymer for use herein is CARBOPOL 956, commerciallyavailable from Lubrizol, and having a viscosity as measured on aBrookfield RVT at 20 rpm, neutralized to pH 7.3-7.8 with 0.5% wt %mucilage and a spindle #6 of from 20,7000 to 41,300 at 25° C. Otherexamples of commercially available materials useful herein includeCARBOPOL 980 NF, CARBOPOL 974P NF, CARBOPOL 984 EP, CARBOPOL ULTREZ 10NF, CARBOPOL 971P NF, and combinations thereof.

In an example, the adhesive-building polymer is selected from highmolecular weight homo and co-polymers of acrylic acid crosslinked with apolyalkenyl polyether, and mixtures thereof.

Other adhesive-building polymers useful herein include the EUDRAGITseries of polymethacrylate-based copolymers. The series includesanionic, cationic, and neutral copolymers based on methacrylic acid andmethacrylic/acrylic esters or their derivatives. Such polymers arecommercially available from Evonik (Essen, Germany).

Other examples of adhesive-building polymers useful herein include PVP,polymers having a polycarboxylated ethylene backbone (e.g. the GANTREZ,ACUSOL, or SOKALAN series of polymers), poly(2-ethyl-2-oxazoline),polyacrylamide, copolymers with acrylamide, pectin, proteins, highmolecular weight polyethylene glycols (e.g. POLYOX, AQUAZOL), andmixtures thereof.

The GANTREZ series of polymers are copolymers of maleic anhydride withmethyl vinyl ether having a molecular weight (M.W.) of about 30,000 toabout 1,000,000. These copolymers are available for example as GantrezAN 139 (M.W. 500,000), AN 119 (M.W. 250,000) and S-97 PharmaceuticalGrade (M.W. 70,000), from Ashland Chemicals (Kentucky, USA).

The ACUSOL and the SOKALAN series of polymers include homopolymers ofacrylic acid and copolymers of maleic acid and acrylic acid ormethacrylic. Examples are 0:1000 to 1000:0 copolymers of maleic acidwith acrylic acid having a molecular weight (M.W.) of about 2,000 toabout 1,000,000. These copolymers are commercially available as Acusol445 and 445N, Acusol 531, Acusol 463, Acusol 448, Acusol 460, Acusol465, Acusol 497, Acusol 490 from Dow Chemicals (Michigan, USA) and asSokalan CP 5, Sokalan CP 7, Sokalan CP 45, and Sokalan CP 12 S from BASF(New Jersey, USA).

Other examples of adhesive-building polymers useful herein includeethylene oxide polymers, homopolymers or mixtures of ethylene oxidepolymers of varying molecular weight ranging from about 10,000 Daltonsup to about 10,000,000 Daltons, and preferably in the range of about100,000 to about 1,500,000 Daltons. Polyethylene oxide in the molecularweight range of 10,000 to 1,000,000 Daltons is available from the DowChemical Company (Michigan, USA) under the trade name POLYOX.

Other examples of adhesive-building polymers useful herein include PVP,poly(2-ethyl-2-oxazoline), polyacrylamide, copolymers with acrylamide,pectin, proteins, high molecular weight polyethylene glycols (e.g.AQUAZOL from PCI, Inc. Arizona, USA), and mixtures thereof.

One class of polymers that is not recommended for use herein is theblock polypropylene oxide, polyethylene oxide copolymers sold under thetrade name PLURONICS by BASF (New Jersey, USA).

Secondary Structuring Polymer

The desensitizing oral care compositions may include a water-soluble,water swellable or water hydratable secondary structuring polymer. Thecompositions contain from about 0.5% to about 40%, by weight of thecomposition, of the secondary structuring polymer. The compositions maycontain from about 1% to about 20%, alternatively from about 1% to about10%, alternatively from about 2% to about 6%, alternatively from about2.5% to about 5.5%, by weight of the composition, of the secondarystructuring polymer.

“Secondary structuring polymer” as used herein refers to awater-soluble, water swellable or water hydratable polymer that, whenused in the compositions of the present invention, is capable ofproviding the delta angle value parameter needed and/or providingviscoelastic properties suitable for the benefits desired such asreducing gel flow off the strip, or releasing from a release liner orother applicator in one piece (or at least partially releasing).

The secondary structuring polymer may be selected from polycarboxylates,carboxylate-substituted polymers, and mixtures thereof.

Examples of secondary structuring polymers useful herein includepolysaccharides. An example secondary structuring polymer is acarboxymethyl polysaccharide. The secondary structuring polymer may beselected from cellulosic polymers, preferably derivatized cellulosicpolymers, preferably carboxylate derivatized cellulose, preferablycarboxymethylcellulose.

The secondary structuring polymer may be selected fromcarboxymethylcellulose, dextran, starch, pectins, and mixtures thereof.The secondary structuring polymer can be a sodiumcarboxymethylcellulose.

The secondary structuring polymer can be selected fromhydroxyethylcellulose, hydroxypropylcellulose,hydroxypropylmethylcellulose, methylcellulose, ethylcellulose,cellulose, sodium carboxymethylcellulose, corn starch, and mixturesthereof.

The carboxymethylcellulose can be selected front those having from about0.5 to about 1.5 degrees of substitution, preferably about 0.65 to about0.75 degrees of substitution. In an example, the carboxymethylcellulosehas a viscosity in a 2% solution with water of from about 100 to about1500 milliPascals (mPas), alternatively from about 100 to about 900mPas, alternatively from about 200 to about 800 mPas. Preferably thesecondary structuring polymer is food grade. Preferably thecarboxymethylcellulose is of smooth type.

Examples of specific grades of useful carboxymethylcellulose includeAQUALON 7M8SF, commercially available from Hercules (Delaware, USA),having a viscosity of a 2% solution in water of 200-800 mPas and adegree of substitution of from about 0.65 to about 0.9. The overallAQUALON 7M series has a viscosity in a 2% solution of water of fromabout 100 to about 1800 mPas with a degree of substitution of from about0.65 to about 0.9 and the AQUALON 7H series has a viscosity in 1%solution of water from about 1000 to about 6000 mPas, also with a degreeof substitution of from about 0.65 to about 0.9. The overall AQUALON 9Hfood grade series of carboxymethylcellulose has a viscosity of from2500-6000 milliPascals, and a degree of substitution of from about 0.80to about 0.95. A combination of polymers from within or between theAQUALON 7H and AQUALON 9H series may be used.

Optional Additional Thickener

In addition to the adhesive-building polymer and secondary structuringpolymer, the compositions herein may further include an additionalthickener that is compatible with the polymers, desensitizing agent, andother components. Examples of additional thickeners useful hereininclude gums, resins, alginates, carrageenan, gelatin, algin, chitosan,polyamines, polyquaternary compounds, and mixtures thereof. Gums usefulherein include xanthan gum, karaya gum, guar gum, gum arabic, gumtragacanth, and mixtures thereof. Polyols such as sorbitol and glycerinmay help build the thickness of adhesive-building polymers. A preferredadditional thickener is xanthan gum.

Plasticizer/Humectant

The desensitizing compositions may include from about 1% to about 40%,by weight of the composition, of a humectant, sometimes referred to inthe literature as a plasticizer. The composition may contain from about5% to about 40%, alternatively from about 10% to about 40%,alternatively from about 20% to about 35%, alternatively from about 25%to about 35%, alternatively about 30%, by weight of the composition, ofa humectant.

Humectants useful herein include, for example, glycols such as propyleneglycol, polyethylene glycol, polyhydric alcohols such as glycerin andsorbitol and glycerol esters such as glycerol triacetate. Glycerin canbe used as well as propylene glycol or polyethylene glycol such as isavailable from Union Carbide Corporation as their series of CARBOWAXmaterials that range in molecular weight from 200 to 600 Daltons. Otherplasticizers include cellulose esters, sebacate esters, castor oil,tricresyl phosphate, and pthalate adipate. The plasticizer can beglycerin.

Other Oral Care Actives/Materials

In addition to the desensitizing agent, other oral care actives (ormaterials) may be included in the desensitizing compositions herein.Suitable oral care actives generally include any material that isgenerally considered as safe for use in the oral cavity that providesbeneficial changes to the oral cavity, and in an example, improves thecondition of the oral surfaces the oral care composition contacts.

Optional materials include, for example, flavoring agents, dyes(including hueing dyes such as those in the blue or violet spectrum),sweetening agents, xylitol, opacifiers, and coloring agents. Flavorantswhich may also function as TREK agonists may be preferred for addeddesensitizing activity; these include Spearmint oil, Wintergreen oil,thymol, eugenol, and combinations thereof.

Optional oral care actives useful herein include many of the activespreviously disclosed in the art such as teeth whitening actives,phosphates (for anti-tartar benefits), fluoride ion sources,antimicrobial agents, anti-inflammatory agents, nutrients, enzymes,anti-fungals, antibiotics, analgesic agents, antioxidants, H-2antagonists, and combinations thereof. A more extensive description ofsuch actives may be found in U.S. Pat. No. 6,136,297 assigned to theProcter & Gamble Company.

In an example, the desensitizing composition further includes awhitening active. Whitening actives useful herein include peroxides,metal chlorites, perborates, percarbonates, peroxyacids, and combinationthereof. Suitable peroxide compounds include hydrogen peroxide, calciumperoxide, carbamide peroxide, and mixtures thereof. Suitable metalchlorites include calcium chlorite, barium chlorite, magnesium chlorite,lithium chlorite, sodium chlorite, and potassium chlorite. Additionalwhitening actives include hypochlorite and chlorine dioxide.

Composition Applied to the Strip of Material

The desensitizing composition can be applied to at least one side of thestrip of material. The strip of material may be manufactured and thenthe composition applied (such as by spray-drying and/or extrusion),and/or the composition may be applied during the manufacture of thestrip of material, such as by co-extrusion. The composition may beapplied to the oral surface and the strip of material applied over thecomposition.

The amount of composition applied to the strip of material or oralsurface depends upon the size and capacity of the material,concentration of the active, and the desired contact time in the oralcavity. Generally, less than about 1 gram of oral care composition isrequired. Preferably, from about 0.001 grams to about 0.5 grams, andmore preferably from about 0.01 gram to about 0.4 grams of the oral carecomposition is used. The amount of oral care composition per square cmof material is less than about 0.5 grams/cm², preferably from about0.0005 to about 0.1 grams/cm², and more preferably from about 0.001grams/cm² to about 0.04 grams/cm².

Release Liner

The delivery systems herein optionally include a release liner. Therelease liner may be a fluoropolymer coated polypropylene film. Examplesof such a film include the SCOTCHPACK 9741 RELEASE LINER commerciallyavailable from 3M (Minnesota, USA). Preferably, there is a minimumborder of the release liner available as “overage” to the strip ofmaterial and/or composition, to allow the user to grab onto the stripand pull the strip off the release liner before use.

The release liner may be formed from any material which exhibits lessaffinity for the desensitizing composition than the desensitizingcomposition exhibits for itself and for the strip of material. Therelease liner preferably comprises a relatively rigid sheet of material(compared to the strip of material) such as polypropylene, paper,polyester, or other material which is then coated with a non-stick typematerial or sacrificial release coating. The release liner material maybe coated with wax, silicone, teflon, fluoropolymers, or other non-sticktype materials. A preferred release liner is Scotchpak®, produced by 3M.As shown in FIGS. 4-6, the release liner 70 may be cut to substantiallythe same size and shape as the strip of material 60 or the release liner70 may be cut larger than the strip of material 60 to provide a readilyaccessible means for separating the material from the strip. The releaseliner may be formed from a brittle material which cracks when the stripis flexed or from multiple pieces of material or a scored piece ofmaterial. Alternately, the release liner 70 may be in two overlappingpieces, 70A and 70B, with overlapping area 80, such as a typicaladhesive strip bandage design. A further description of materialssuitable as release agents is found in Kirk-Othmer Encyclopedia ofChemical Technology, Fourth Edition, Volume 21, pp. 207-218,incorporated herein by reference.

Preferably, a release liner is used to present the sensitivity treatmentstrip to the consumers. The adhesive matrix coated strip is placed onthe release liner such that the adhesive matrix is between the strip ofmaterial and the release liner. When removing the strip an adhesivematrix from the release liner, it is preferable to have most or all ofthe adhesive matrix remain with the strip of material. In order for thisto be the case, the adhesive matrix should have more affinity for thestrip of material than the release liner. In addition, the adhesivematrix must have sufficient internal strength or cohesion such that thegel does not shear leaving some adhesive matrix on the strip and some ofthe release liner. Without being limited by theory, it was surprisinglylearned that when using just one adhesive-building polymer, such ase.g., CARBOPOL, the strip of material and composition may notsufficiently release off the release liner. Using just a secondarystructuring polymer, such as, e.g., CMC, the product releases, but maylack sufficient adhesion in-vivo. An adhesive-building polymer and astructuring polymer combined may be needed to provide an acceptablebalance of release and adhesion.

Physical stability of the composition on the strip of material onceapplied to the release liner can also be important. Specifically, oncethe strip of material and composition are applied to the release liner,it is desirable to have the adhesive matrix remain within the perimeterof the strip, meaning, e.g. it does not flow significantly outside theboundaries of the strip. Flowing outside the boundaries of the strip maycreate an undesirable situation with respect to the packaging of thestrip, for example in a pouch. In this case, the gel which has flowedoutside of the perimeter of the strip can adhere the strip to the insideof the pouch making it difficult to remove before use. With otherpackaging such as, e.g., a tray and cover, this may be of less concern.

Packaging

The delivery system may be packaged in any package suitable forproviding a moisture barrier. One example is a foil laminate pouch,another is a plastic tray.

Methods of Use

Methods of using the desensitizing delivery system set forth herein totreat the oral cavity (or portions thereof) before or after the use of awhitening delivery system (such as a commercially available whiteningstrip product like CREST WHITESTRIPS) are also contemplated herein.

In practicing the present invention, a strip of material may be appliedto the desired oral surface by the wearer. The side of the materialfacing the oral surface is at least the side wherein the compositionherein is applied. This oral care composition provides a vehicle for theactive as well as tackiness between the oral surfaces and the strip ofmaterial, holding the strip of material in place for extended periods oftime. The period over which the strip of material is used may be, forexample, from about one to about thirty minutes.

The strip of material may readily conform to the oral care surface bylightly pressing it there against, e.g., under light to moderate fingerpressure. The strip of material is easily removed by the wearer bypeeling it off using a finger or fingernail. Preferably each successivetreatment uses a fresh strip of material.

In the situation were the oral care surface is the surface of teeth, itmay be unnecessary to prepare the teeth surface before applying thedelivery system of the present invention. For example, the wearer may ormay not choose to brush his teeth or rinse his mouth before applying thedelivery system. The surfaces of the teeth are not required to be driedor to be excessively wet with saliva or water before the strip ofmaterial is applied.

When the wearer removes the strip of material from the oral surface,there may be a residual amount of oral care composition remaining on thesurface. The amount residual oral care composition, however, may not begreat in embodiments where the oral care composition has affinity forboth the strip of material (e.g., adhesion to the delivery strip) andfor itself (e.g., cohesion). Any residual oral care composition may beeasily removed by wiping, brushing or rinsing the oral surface.

The delivery system herein may optionally be applied with two fingers tothe oral surface in need of treatment. The delivery system may beallowed to remain in place for at least five minutes. The deliverysystem may be applied to cover at least a portion of a tooth and atleast a portion of the adjoining soft tissue (gum) area.

EXAMPLES

Testing Methodology

Complex Modulus and Delta Angle

To measure the complex modulus (G*) and delta angle of a compositionaccording to the present invention, the following procedure is used. AnAdvanced Rheometer 2000 (AR2000, TA Instruments, New Castle, Del.)equipped with a stainless steel cone and plate fixture is provided. Thecone and plate diameter used is 40 mm with a cone angle of 2 degrees.The testing is conducted at room temperature, approximately 25 degreesC. After the fixture is installed and the instrument initialized, anexcess amount of the bulk composition is placed on the bottom plate andthe cone is lowered into the composition to a final gap of 0.048 mmExcess composition will extrude from the gap between the cone and plateand must be removed without pulling material from out of the gap.Approximately 0.6 mL of the composition remains between the cone andplate. The instrument is set to perform oscillatory strain cycles withthe following parameters:

Duration of Run: 30 minutes

Applied Strain: 1%

Frequency: 1 Hz

Sample Points per run: 15

The data is analyzed using TA Instrument's software, TA RheologyAdvantage Data Analysis version 5.7.0. The software is used to generateplots of either complex modulus or delta angle versus time and the meanvalue for the period 1 to 30 minutes is determined.

To determine the low shear viscosity, the same rheometer, rheometertooling, gap, and software are used. The procedure for measuring the lowshear viscosity is as follows: After sample loading/trimming, conditionsample at 25° C. for 10 minutes. Conduct a steady state Stress ramp from2-200 Pa at 25° (Log mode, 10 points/decade, 5% tolerance). Thencondition at 25° C. for 2 minutes. Then Continuous Ramp shear rate from0.1-100 sec⁻¹ (Log mode, 5 minute test, 10 points/decade). Then plot LogViscosity (y axis) vs. Log Shear Rate (x axis). Visually assess plot anddetermine viscosity in the low shear rate plateau region.

Example 1

Compositions according to the present invention were made according tothe formulations set forth in Tables 1A through 1D, below.

Comparative Examples were made according to the formulations set forthin Tables 2A through 2B, below.

As may be seen in the results shown in Tables 1A through 1B=D, whencompared to the results presented in Tables 2A and 2B, and graphicallyrepresented in FIG. 1 attached herein, compositions according to thepresent invention, when applied to a strip of material and a releaseliner were found to provide sufficient adherence in-vivo, refrain fromsignificant gel flow off the strip during storage, and release themajority of the oral care composition gel from the release liner.

Examples of desensitizing compositions according to the presentinvention are found below in Tables 1A, 1B, 1C, and 1D. Comparativeexamples of desensitizing compositions are found in Tables 2A and 2B.The compositions were compounded using either a Ross double planetarymixer LDM-2 or Ross double planetary mixer DPM-40. Glycerin was weighedand added to a clean Ross mix tank. Water was weighed and added to aseparate stainless steel mix tank equipped with a lightning mixer and 4″diameter turbine mixing blade. The carboxymethyl cellulose and theCARBOPOL were weighed and added to a clean plastic polyethylene bucket.The lid was applied to the bucket and the powders were rotated by handto blend the powders together for 10 minutes. The potassium sorbate,potassium benzoate and potassium oxalate were weighed and added to thewater in the stainless steel mixing tank. The lightning mixer was thenused to completely dissolve the added salts. The sodium hydroxide wasweighed and added to the potassium sorbate/sodium benzoate/potassiumoxalate solution in the stainless steel mix tank. The solution was thenmixed until clear. The blended carboxymethyl cellulose and CARBOPOLpowder mix was carefully added to the glycerin by hand adding to coverthe surface of the glycerin uniformly in the Ross mix tank. The Rossmixer was started and ran at a speed setting of 5 for 30 minutes. Thesolution from the stainless steel tank was then added to the Ross mixerand mixing continued for 45 minutes at a speed setting of 5. After thismixing session, the composition was checked for visible lumps. If lumpswere present, the composition was mixed for an additional 20 minutes ata speed setting of 5.

Once the compounding of the composition is complete, strip-type deliverysystems were made by slot coating the composition onto a sheet ofrelease liner made of fluoropolymer coated polypropylene film sold underthe brand name SCOTCHPACK 9741 RELEASE LINER (commercially availablefrom 3M (Minnesota, USA)) and then combined with a polyethylene filmmaterial, an HDPE/LDPE blend polyethylene film (commercially availablefrom Clopay (Cincinnati, USA) as embossed polyethylene film—32 GSMSof-flex) using a continuous lamination process. This resulting laminatewas then run through rotary kiss cutting dies to cut the strip shape to1 cm×3 cm. The polyethylene material outside of the strip perimeter wasremoved and the resultant release liner with 1 cm×3 cm strip spaced outon the web was cut into individual release liners measuring 3 cm×9 cm.The individual release liners with strips were placed into foil laminatepouches and sealed with heat.

The resulting delivery systems were tested for release off the releaseliner and gel flow and the Complex Modulus and Delta were measured andcalculated pursuant to the methods set forth herein. Some products werefurther tested for in vivo adhesion and the results included below. Todetermine release off the liner, the strip was removed from the foillaminate pouch and the strip and laminated composition were graspedbetween two fingers and pulled from the release liner at a rate ofapproximately 3 cm/sec. The percentage amount of composition remainingon the release liner was visually analyzed and recorded. In vivoadhesion was determined by a wear panel.

The delivery systems with the compositions shown in Table 1A, 1B, 1C,and 1D are according to the invention set forth herein. As may be seenby the data tabulated in the Tables below, compositions 1a through 1twere found to perform acceptably in all categories tested. Those in 1mand 1n as well as 1p through 1t include an optional additionalthickener, xanthan gum.

Comparative delivery systems are shown and the data associated therewithare tabulated below in Tables 2A, 2B. Such comparative delivery systems,where tested, exhibited at least one unacceptable characteristic thatmake them less suitable for treating dentinal hypersensitivity.

FIG. 1 plots the Complex Modulus versus the Delta value for thecompositions shown in Tables 1A, 1B, 1C, 1D as well as 2A and 2B. As maybe seen in FIG. 1, the example formulations in 1A, 1B, 1C and 1D meetEquation 1 (indicated by the solid black line), while 2A and 2B falloutside the desired relationship. Equation 2 is shown as a dotted blackline.

TABLE 1A Desensitizing Oral Care Compositions 1a 1b 1c 1d 1e IngredientWt. % Wt. % Wt. % Wt. % Wt. % Carboxymethyl 5.0 5.0 4.5 4.5 4.0Cellulose 7M8SF Glycerin USP (99.7) 31.86 31.86 31.86 31.86 31.86CARBOPOL 956 1.0 1.0 2.5 2.5 2.5 Sodium Benzoate, NF FCC 0.50 0.5 0.50.5 0.5 Potassium Sorbate 0.20 0.2 0.2 0.2 0.2 Sodium Hydroxide 0.250.25 1.1 1.05 1.0 Solution 50 Potassium Oxalate 3.14 3.14 3.14 3.14 3.14Monohydrate, ACS Purified Water USP 58.05 58.05 56.2 56.25 56.8 TESTRESULTS: Complex Modulus (G*) 709 860 1085 908 883 Delta (Degrees) 27.220.2 23.8 22.7 24.2 1700 e ^((−0.05 Delta Angle)) 436.3233 619.1723517.1761 546.4176 506.9354 (Equation 1) 2100 e ^((−0.05 Delta Angle))538.9876 764.8599 638.8647 674.9865 626.2143 (Equation 2) Release fromRelease Liner 100 100 95 * 100 (%) Gel Flow off strip No * No No NoAdheres in-vivo Yes * Yes Yes Yes Carboxymethyl Cellulose 7M8SF, 9H, and7H are part of the AQUALON series commercially available from Hercules.CARBOPOL 956 is commercially available from Lubrizol. *Data point notcollected for sample.

TABLE 1B Desensitizing Oral Care Compositions 1f 1g 1h 1i 1j IngredientWt. % Wt. % Wt. % Wt. % Wt. % Carboxymethyl 4.5 4.5 4.5 4.5 4.5Cellulose 7M8SF Glycerin USP (99.7) 31.86 31.86 31.86 31.86 31.86CARBOPOL 956 2.0 2.0 2.0 2.0 2.0 Sodium Benzoate, NF FCC 0.5 0.5 0.5 0.50.5 Potassium Sorbate 0.2 0.2 0.2 0.2 0.2 Sodium Hydroxide 0.75 0.750.75 0.75 0.75 Solution 50 Potassium Oxalate 3.14 3.14 3.14 3.14 3.14Monohydrate, ACS Purified Water USP 57.05 57.05 57.05 57.05 57.05 TESTRESULTS: Complex Modulus (G*) 855.4 874 1093 1108 1049 Delta (Degrees)25.2 25.6 18.4 18.5 19.2 1700 e ^((−0.05 Delta Angle)) 482.2118 472.6634677.4824 674.1034 650.9179 (Equation 1) 2100 e ^((−0.05 Delta Angle))595.6735 583.8783 836.89 832.716 804.0751 (Equation 2) Release fromRelease Liner 100 100 100 100 100 (%) Gel Flow off strip No No * * *Adheres in-vivo Yes Yes * * * Carboxymethyl Cellulose 7M8SF, 9H, and 7Hare part of the AQUALON series commercially available from Hercules.CARBOPOL 956 is commercially available from Lubrizol. *Data point notcollected for sample.

TABLE 1C Desensitizing Oral Care Compositions 1k 1l 1m 1n 1o IngredientWt. % Wt. % Wt. % Wt. % Wt. % Carboxymethyl 5.0 5.0 4.0 2.5 5.0Cellulose 7M8SF Glycerin USP 99.7 31.86 31.86 31.86 31.86 31.86 CARBOPOL956 1 1.0 1.0 2.5 1.5 Xanthan Gum, NF 1.0 2.5 Sodium Benzoate, NF FCC0.5 0.5 0.5 0.5 0.5 Potassium Sorbate 0.2 0.2 0.2 0.2 0.2 SodiumHydroxide .25 0.25 0.25 1.2 0.5 Solution 50 Potassium Oxalate 3.14 3.143.14 3.14 3.14 Monohydrate, ACS Purified Water USP 58.05 58.05 58.0555.6 57.3 TEST RESULTS: Complex Modulus (G*) 1087 2912 664 1357 993Delta (Degrees) 27.9 12.6 24.4 16.3 20.8 1700 e ^((−0.05 Delta Angle))421.3162 905.4061 501.8913 752.4869 600.873 (Equation 1) 2100 e^((−0.05 Delta Angle)) 520.4494 1118.443 619.9834 929.5426 742.2548(Equation 2) Release from Release Liner No data 100 100 98 100 (%) GelFlow off Strip No No No No * Adheres in-vivo Poorly Poorly * * *Carboxymethyl Cellulose 7M8SF, 9H, and 7H are part of the AQUALON seriescommercially available from Hercules. CARBOPOL 956 is commerciallyavailable from Lubrizol. *Data point not collected for sample.

TABLE 1D Desensitizing Oral Care Compositions 1p 1q 1r 1s 1t 1u Wt. %Wt. % Wt. % Wt. % Wt. % Wt. % Ingredient Carboxymethyl 3.0 3.0 3.0 3.53.5 5.0 Cellulose 7M8SF Glycerin USP 99.7 31.86 31.86 31.86 31.86 31.8631.86 CARBOPOL 956 2.0 2.0 2.5 2.5 2.5 5 Xanthan Gum, NF 1.5 2.0 1.0 1.01.0 Sodium Benzoate, NF 0.5 0.5 0.5 0.5 0.5 0.5 FCC Potassium Sorbate0.2 0.2 0.2 0.2 0.2 0.2 Sodium Hydroxide 0.75 0.75 1.0 1.0 1.05 Solution50 Potassium Oxalate 3.14 3.14 3.14 3.14 3.14 3.14 Monohydrate, ACSPurified Water USP 56.7 56.55 56.8 56.3 56.25 54.3 TEST RESULTS: ComplexModulus 794 920 877 1041 849 3131 (G*) Delta (Degrees) 21.6 20.6 21 21.420.7 16.3 1700 e^((−0.05 Delta Angle)) 577.3124 606.9118 594.8942583.1145 603.8848 752.4869 (Equation 1) 2100 e^((−0.05 Delta Angle))713.1506 749.7146 734.8693 720.3179 745.9754 929.5426 (Equation 2)Release from Release 95 95 100 100 100 99 Liner (% Released) Gel Flowoff Strip No No No No No * Adheres in-vivo Yes Yes Yes Yes Yes *Carboxymethyl Cellulose 7M8SF, 9H, and 7H are part of the AQUALON seriescommercially available from Hercules. CARBOPOL 956 is commerciallyavailable from Lubrizol.

TABLE 2A Comparative Desensitizing Oral Care Compositions 2a 2b 2c 2d 2eIngredient Wt. % Wt. % Wt. % Wt. % Wt. % Carboxymethyl 2.5 2.5 1 2Cellulose 7M8SF Glycerin USP 99.7 31.86 31.86 31.86 31.86 31.86 CARBOPOL956 5.0 2.5 2.5 1.0 3.0 Sodium Benzoate, NF FCC 0.5 0.5 0.5 0.5 0.5Potassium Sorbate 0.2 0.2 0.2 0.2 0.2 Potassium Oxalate 3.14 3.14 3.143.14 3.14 Monohydrate, ACS Purified Water USP 57.3 59.3 59.3 62.3 59.3TEST RESULTS: Complex Modulus (G*) 1148 422 486 25 501 Delta (Degrees)6.1 25.4 23.7 33 21.8 1700 e ^((−0.05 Delta Angle)) 1253.11 477.4138519.7685 326.4848 571.568 (Equation 1) 2100 e ^((−0.05 Delta Angle))1547.959 589.7464 642.067 403.3048 706.0546 (Equation 2) Release fromRelease Liner 20 50 75 0 30 (% Released) Gel Flow off Strip * * * * *Adheres in-vivo * * * * * Carboxymethyl Cellulose 7M8SF, 9H, and 7H arepart of the AQUALON series commercially available from Hercules.CARBOPOL 956 is commercially available from Lubrizol. *Data point notcollected for sample.

TABLE 2B Comparative Desensitizing Oral Care Compositions 2g 2h 2i 2jIngredient Wt. % Wt. % Wt. % Wt. % Carboxymethyl Cellulose 0 0 0 0Glycerin USP 99.7 31.86 31.86 31.86 31.86 CARBOPOL 956 1.0 4.5 2.0 1.0Xanthan Gum, NF 5.0 Sodium Benzoate, NF 0.5 0.5 0.5 0.5 FCC PotassiumSorbate 0.2 0.2 0.2 0.2 Sodium Hydroxide 0.25 2.0 0.75 0.25 Solution 50Potassium Oxalate 3.14 3.14 3.14 3.14 Monohydrate, ACS Purified WaterUSP 58.05 57.80 61.55 63.05 TEST RESULTS: Complex Modulus (G*) 1033 81071 0.3 Delta (Degrees) 7.6 7.6 9.1 74.9 Release from Release 30 30 0 0Liner (% Released) 1700 e ^((−0.05 Delta) ^(Angle)) 1162.564 1162.5641078.562 40.18057 (Equation 1) 2100 e ^((−0.05 Delta) ^(Angle)) 1436.1091436.109 1332.341 49.63482 (Equation 2) Gel Flow off Strip * * * YesAdheres in-vivo No No No Carboxymethyl Cellulose 7M8SF, 9H, and 7H arepart of the AQUALON series commercially available from Hercules.CARBOPOL 956 is commercially available from Lubrizol. *Data point notcollected for sample.

Example 2

Seven individual panelists participated in a qualitative usage study of5 sensitivity strips. Each panelist was asked to wear 3 of the 5 strips.Panelists were instructed to apply one strip to the outside molars ofone quadrant (upper or lower) of their teeth for 10 minutes while atwork during business hours (between 9 am and 3 pm). To test the ease ofapplication and fit during use, panelists applied strips to the backmolars as this has been identified as the most difficult location toapply and wear the strips. Panelists were instructed to remove the stripand asked to respond to a questionnaire. Panelists recorded evaluations(shown in Table 3) for wearing, positioning, using, “stickiness”, andpeeling. Each panelist was asked to repeat the process with a total ofnine strips. The only difference between the strips was the length ofthe strip.

TABLE 3 Qualitative Evaluation of Strip Length 3.0 cm 4.0 cm 4.5 cm 5.0cm 6.0 cm Base Size 13 13 13 12 13 Ease of handling strip with fingers0.753 0.495 0.240 −0.473 −0.851 (Scale +4 to −4: +4 = Like mostpossible, 0 = Netural, −4 = Dislike most possible) Ease of positioningon desired area 0.906 0.880 0.799 −0.858 −0.699 (Scale +4 to −4: +4 =Like most possible, 0 = Netural, −4 = Dislike most possible) Stripstaying in place the entire time 0.288 1.628 1.658 0.350 0.893 (Scale +4to −4: +4 = Like most possible, 0 = Netural, −4 = Dislike most possible)Ease of removing the strip 1.314 2.050 1.934 1.671 2.052 (Scale +4 to−4: +4 = Like most possible, 0 = Netural, −4 = Dislike most possible)The size of the strip while handling prior to use −0.627 −0.132 0.2680.693 1.090 (JAR Scale: −2 = Too small, 0 = Just Right, +2 = Too large)The coverage of the strip in mouth during use −0.742 0.024 0.411 0.7910.965 (JAR Scale: −2 = Too small, 0 = Just Right, +2 = Too large)

Example 3

Dentinal Flow Rate Measurement

Volumetric flow rates through cross-sections of human 3^(rd) molarcoronal dentin are measured before and after treatment using a flow cellapparatus (FIG. 6). Twenty two coronal dentin sections of human molarsare obtained by cross sectional cutting with a diamond blade saw to athickness between 0.80 and 1.00 mm. The sections resemble disks due tothe circular nature of molars. The center of the disk is dentin 90 witha thin ring of enamel around the circumference (FIG. 6). The cut dentindisks are then placed in 6.0% citric acid for two minutes followed bysonication in water and subsequent rinsing to remove the smear layercreated by the cutting process. The removal of the smear layer withcitric acid is an effective and well known technique to produce opendentinal tubules representative of sensitive dentin found in-vivo.Samples are then immersed in at least 10 ml of commercial phosphate (pH7) buffer for storage at neutral pH until needed.

For treatment, each dentin section 90 is mounted in a Pashley-likeliquid flow cell testing apparatus, as shown in FIGS. 7-8. Each dentindisk section is centered over the opening with flat washers 110 andbushing 120 on each side, making sure that the section spanned theopening with at least 1 mm overlap around the entire perimeter. Once thedentin sections are appropriately positioned, the flow cell assemblyscrews are tightened to hold the section in place and ensure no leakagearound the rubber washers. All washers are cut with an outer diameter of¾″. The inner diameter for the bottom rubber washer is ¼″ and thesilicone washer on the top is ⅜″. After mounting, each dentin sectionundergoes the following treatment sequence (1) conditioning, (2)baseline flow measurement, (3) treatment, and (4) post-treatment flowmeasurement.

-   (1) Conditioning: Hartmann's solution is applied to the dentin    section at 30 psi against the non-treatment side for 45 minutes to    equilibrate the dentin disk with a solution isotonic with pulpal    fluid. Next, the treatment surface of each dentin section is brushed    with a toothbrush for 8 minutes with Hartmann's solution while    rotating the entire cell apparatus 90 degrees every 60 seconds and    re-wetting the toothbrush with Hartmann's solution every 30 seconds.    Each specimen is then allowed to equilibrate for 5 minutes with    Hartmann's solution flowing through the section at 30 psi.-   (2) Baseline Flow Measurement: A bubble is introduced into the    beginning of the supply line tubing of the flow cell apparatus by    releasing the pressure, loosening the fittings and raising the    tubing above the flow cell test apparatus. The fittings are then    retightened and 30 psi pressure is re-applied. The liquid velocity    is recorded by timing the movement of the bubble within the supply    line. The supply line is run across a light box and parallel to a    precision ruler. Using a digital stop watch, elapsed times are    recorded over 4 equidistant points along the ruler to establish the    average rate the bubble travels and to ensure the velocity is    constant. The linear rates are converted to volumetric flow rates by    multiplying by 11.6 μl/in for 0.030″ ID tubing of the supply line.    Consecutive flow measurements are taken until 2 consecutive    measurements vary by less than 5% to establish the baseline flow    rate.-   (3) Treatment: After conditioning each dentin section, the inlet    fluid is switched from Hartmann's solution to an artificial pulpal    fluid and allowed to flow through each section from the    non-treatment side for 2 min at 30 psi. Next, the pressure is    reduced to 0.43 psi and the flow cell apparatus is tipped 90°. A    Kimwipe is used to absorb fluid as it drains off of the dentin    surface. Note: The Kimwipe is not used to directly wipe the surface    of the dentin section to avoid any surface contamination. All    treatments are then applied directly to the surface of the mounted    dentin disk. After treatment the section is thoroughly rinsed with    Hartmann's solution. The inlet fluid source is then switched from    artificial pulpal fluid back to Hartmann's solution and the flow    cell is flushed by opening a dump valve downstream from the flow    cell apparatus.-   (4) Post Treatment Flow Measurement: For comparison to the baseline    flow measurement, post treatment flow measurements are taken. Each    dentin section is brushed for 2 minutes with Hartmann's solution    while rotating the flow cell 45° every 10 seconds. The sections are    then equilibrated with Hartmann's solution at 30 psi for 2 minutes.    Flow rates are then obtained as described for the baseline flow    measurements.    -   Volumetric flow reductions for each treated dentin disk are        calculated with the following equation:

${\%\mspace{14mu}{Reduction}} = {100*\frac{\left( {Q_{p} - Q_{b}} \right)}{Q_{b}}}$

-   -   Where Q_(p)=average post-treatment flow, and Q_(b)=average        baseline flow.        Preparation of Hartmann's Solution (HS) (1 L)        Composition: 30 mM lactic acid, 2 mM CaCl₂, 5 mM KCl, 100 mM        NaCl    -   1. Add the following to a 1 L beaker:        -   3.38 g lactic acid        -   0.294 CaCl₂.2H₂O        -   0.373 g KCl        -   5.844 g NaCl    -   2. Add approximately 600 mL of deionized water and stir until        dissolved    -   3. Adjust the pH to 7.0 (6.5-7.5) using concentrated NaOH, then        transfer to a 1 L volumetric flask    -   4. Fill to volume with deionized water and record final pH    -   5. Solution expires 6 months from making, stored at room        temperature.        Preparation of Artificial Pulpal Fluid (APF) (100 mL)    -   1. Add 1.20 g of Bovine Serum Albumin (BSA) to a 100 mL        volumetric flask.    -   2. Add ˜50 mL of Hartmann's solution, swirl gently to solubilize        albumin Make up volume (to 100%) with Hartmann's solution and        invert gently to mix.    -   3. Solution should be stored refrigerated and used within 2 days        of making.

Reagents Suggested Type or Source Bovine Serum Albumin Sigma p/nA2153-100G NaCl Sigma p/n 71379-500G KCl EMD p/n PX1405-1 Lactic Acid80% Sigma p/n 27715 CaCl₂•H₂O Sigma p/n C3881-500G NaOH 50% JT Baker p/n3727-01

Example 4

An aqueous solution containing 3.14% potassium monohydrate and 1.5%oxalate ion (wt/wt) was tested according to the method of Example 3,except that the treatment time was extended to 10 minutes. Samples werevaried by pH. A strong pH-dependence was observed, with solutions havinga pH less than 4.5 essentially eliminating pulpal flow. The results areshown graphically in FIG. 9.

The dimensions and values disclosed herein are not to be understood asbeing strictly limited to the exact numerical values recited. Instead,unless otherwise specified, each such dimension is intended to mean boththe recited value and a functionally equivalent range surrounding thatvalue. For example, a dimension disclosed as “40 mm” is intended to mean“about 40 mm” The compositions herein can comprise, consist essentiallyof or consist of the materials set forth herein.

Every document cited herein, including any cross referenced or relatedpatent or application and any patent application or patent to which thisapplication claims priority or benefit thereof, is hereby incorporatedherein by reference in its entirety unless expressly excluded orotherwise limited. The citation of any document is not an admission thatit is prior art with respect to any invention disclosed or claimedherein or that it alone, or in any combination with any other referenceor references, teaches, suggests or discloses any such invention.Further, to the extent that any meaning or definition of a term in thisdocument conflicts with any meaning or definition of the same term in adocument incorporated by reference, the meaning or definition assignedto that term in this document shall govern.

While particular embodiments of the present invention have beenillustrated and described, it would be obvious to those skilled in theart that various other changes and modifications can be made withoutdeparting from the spirit and scope of the invention. It is thereforeintended to cover in the appended claims all such changes andmodifications that are within the scope of this invention.

What is claimed is:
 1. A desensitizing oral care composition useful fortreating dentinal hypersensitivity, comprising: a) at least 40%, byweight of the composition, of water; b) from about 0.01% to about 25%,by weight of the composition, of a desensitizing agent selected fromoxalic acid, salts of oxalic acid, and mixtures thereof; c) from about0.1% to about 30%, by weight of the composition, of an adhesive polymerthickener; d) from about 0.5% to about 40%, by weight of thecomposition, of a secondary structuring polymer thickener; e) optionallyfrom about 10% to about 40%, by weight of the composition, of ahumectant; and f) less than 0.1%, by weight of the composition, ofabrasive; wherein the composition has a pH of less than 4.5; wherein thecomposition exhibits a delta angle value of less than about 35°; andwherein the complex modulus is according to Equation 1:Complex Modulus≧1700e ^((−0.05 Delta Angle))  (Equation 1).
 2. Acomposition according to claim 1 wherein the composition comprises atleast 50%, by weight of the composition, of water.
 3. A compositionaccording to claim 1 wherein the composition comprises from about 1% toabout 10% of the desensitizing agent.
 4. A composition according toclaim 1 wherein the composition comprises from about 0.5% to about 10%of the adhesive polymer.
 5. A composition according to claim 1 whereinthe composition comprises at least 30% of the humectant.
 6. Acomposition according to claim 5 wherein the humectant comprisesglycerin.
 7. A composition according to claim 1 wherein the ComplexModulus is according to Equation 2:Complex Modulus≧2100e ^((−0.05 Delta Angle))  (Equation 2).
 8. Acomposition according to claim 7 wherein the composition comprises aDelta angle less than 32°.
 9. A composition according to claim 8 whereinthe composition comprises a Delta angle less than 30° and greater than15°.
 10. A composition according to claim 1 wherein the compositioncomprises the secondary structuring polymer in an amount equal to orgreater than the amount of adhesive-building polymer.
 11. A compositionaccording to claim 10 wherein the ratio of the adhesive polymer to thesecondary structuring polymer is from about 1:1 to about 1:5.
 12. Acomposition according to claim 1 wherein the composition furthercomprises sodium hydroxide.
 13. A composition according to claim 1wherein the composition comprises from about 1% to about 6% of thedesensitizing agent.
 14. A composition according to claim 13 wherein thedesensitizing agent is selected from potassium oxalate salts andmixtures thereof.
 15. A composition according to claim 14 wherein thedesensitizing agent is dipotassium oxalate.
 16. A composition accordingto claim 15 wherein the humectant is glycerin.
 17. A compositionaccording to claim 1 wherein the adhesive-building polymer is selectedfrom high molecular weight homo and co-polymers of acrylic acidcrosslinked with a polyalkenyl polyether, and mixtures thereof.
 18. Acomposition according to claim 17 wherein the secondary structuringpolymer is selected from carboxymethylcelluloses and mixtures thereof.19. A desensitizing oral care composition useful for treating dentinalhypersensitivity, comprising: a) from about 50% to about 65%, by weightof the composition, of water; b) from about 1% to about 5%, by weight ofthe composition, of a desensitizing agent selected from oxalic acid,potassium salts of oxalic acid, and mixtures thereof; c) from about 0.5%to about 10%, by weight of the composition, of an adhesive polymerthickener; d) from about 1% to about 20%, by weight of the composition,of a secondary structuring polymer thickener; e) from about 25% to about40%, by weight of the composition, of a humectant; and g) less than0.1%, by weight of the composition, of abrasive; said composition havinga pH less than 4.5.
 20. A desensitizing oral care composition accordingto claim 19 wherein the composition comprises from about 1% to about 5%of the adhesive polymer thickener and from about 1% to about 10% of thesecondary structuring polymer thickener.